There's currently no method to securely access Proton Drive as a filesystem on Linux.

I request an application that can be used to mount a drive to the filesystem with on-the-fly encryption/decryption.

The application should ensure some level of security, such as not storing the account password on the machine, and requiring 2fa at mount time.

This is because the current mechanism people are using, rclone, is not secure: it is almost trivial for malware to copy the rclone configuration file to obtain the user's Proton password. (It is encrypted using a symmetric encryption, with a static key readily available from the project's source code.)